The black diamond coated polypropylene flow cell has been further improved to eliminate microscopic leaks that develop after extended use. Woods metal encapsulating has improved the thermal properties of the system. A small electrical heater installed on the surface of the reaction region permits calibration and heat capacity measurements. The installation of complete computer control, data collection, and analysis is presently underway. Several biochemical reactions are presently being explored using the instrument. These include clatherin assembly, tRNA,-transferase reactions and ATCase reactions with various substrates. The significance of the project lies in the possibility of detecting new reaction pathways as revealed by the thermal reactions and in the ability to make basic thermodynamic measurements on biological reactions where no other detection system is available. In addition, the direct measurement of the reaction enthalpy in a much more precise method than the determina- tion by using the Van't Hoff method, i.e. measuring of the reaction equilibrium at different temperatures. The reason for this is that the range of temperature, 4 degrees C to 40 degrees C is too small for an accurate determination of the enthalpy. Thus to predict the change in reaction equilibrium, a very important quantity, in for example, drug metabolism, a direct calorimetric measurement is much to be preferred.